This application claims the priority of German application 197 45 656.1-22, filed in Germany on Oct. 16, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a shock absorber for a motor vehicle with a deformation body, which can be deformed in the case of a collision and into the path of which a blocking part protrudes, with which, due to the forces acting during a collision, a plastic deformation of the deformation body is achieved with absorption of the collision energy, it being possible to increase the deformation resistance of the deformation body by directing it into an additional deformation stage.
German Patent Document DE 196 33 110 describes a shock absorber for a bumper of a motor vehicle which includes two deformation elements of differing stiffnesses, which are acted as a function of the collision speed of the vehicle. At a predetermined driving speed, a less stiff deformation element is coupled to a stiffer deformation element, which would not yet be deformed at this driving speed. The stiffer deformation can be moved by a drive system into the deformation system, so that, when required, it can be added precisely at the correct time as a function of the measured collision values. The drive system as well must then be able to withstand the collision stresses, so that this arrangement can be achieved only at relatively great expense, if it is to be capable of functioning.
From German Patent Document DE 41 21 497 C2, a shock absorber with a piston-cylinder system is known, the piston movement of which is triggered upon impact and stopped when the piston attains a high displacement speed, after which the shock absorber absorbs the collision energy through plastic deformation. The piston can be stopped through detector-controlled, radially insertable locking pins or semi-circular locking elements, after which the shock absorber is deformed plastically. As a result, in the case of this shock absorber, only one deformation stage with plastic deformation is available for energy absorption in the case of vehicle collision.
From German Patent Document DE 40 37 101 A1, a shock absorber for a bumper in a motor vehicle is known, the outside pipe of which is deformable, in the case of a vehicle collision, an inertial mass acting on the outside pipe and the inertial induced displacement of the mass bringing about a change in the cross-sectional shape of the outside pipe. It is not possible to adjust the shock absorbing behavior.
In U.S. Pat. No. 3, 789, 948 A1, a shock absorber is described for the front end of a car, the damping spring of which is controlled so that it can be compressed with a low or a high expenditure of force as a function of the speed of the vehicle, as a result of which, in the case of a collision at higher speeds, the effect of the damping spring is maintained for a longer time. In order to change the spring resistance, an expensive adjusting mechanism is proposed here, which is continuously acted upon while the vehicle is in motion and which adjusts the spring resistance to the driving speed.
In U.S. Pat. No. 4,929,008 A1, a shock absorber is described, the collision energy decay of which is accomplished first in a is block, which can be deployed by being filled with gas, then in shear bolts and finally in a damping material, so that up to three damping processes are instituted, one after another, depending upon the force of the impact. The energy absorption is caused here by the initiating forces, and cannot be individually controlled.
It is an object of the invention to provide a deformation resistance for a generic shock absorber, which can be adapted to the impact of the vehicle and realized easily.
This object is accomplished according to preferred embodiments of the present invention by providing an arrangement wherein the blocking body has at least two switched positions, in which it protrudes into the path of movement of the deformation body, as a result of which the deformation body is plastically deformed to a greater or lesser extent due to the forces acting during impact.
In advantageous preferred embodiments of the invention, the crash absorber used in a stringer or a bumper mount is designed to be adjustable in its deformation resistance, before or during a vehicle collision, in response to the severity of the accident sensed by a pre-crash recognition or a vehicle sensor system.
Thus, the blocking part can be controlled through various measured values sensed at the time of collision, on the basis of the resulting crash values, or can be taken into account through a pre-crash recognition which, for example, takes into account the speed of the vehicle, the approach speed of the other object in the collision or its contour; and the deformation behavior of the shock absorber can be adapted to the severity of the accident before the collision.
The displacement of a blocking part into different positions, in which it leads to lesser or greater plastic deformation of the deformation element while absorbing collision energy by extending to different extents into the displacement path of the deformation body, represents a simple solution which can be manufactured cost-effectively for the design of the shock absorber.
The deformation behavior adapted to the collision leads to a reduction in injuries to the occupants, since the energy absorption can be optimized in the shock absorber. Furthermore, the control of the shock absorber can also take into account the crash compatibility of the vehicle with respect to the other vehicle involved, and the repair costs of vehicles equipped with this shock absorber can be positively affected.
A cost-effective design of the shock absorber is achieved through a deformation body, which includes at least two concentrically mounted pipes, which individually or together are prevented from moving by the blocking part, and therefore are plastically deformed upon impact. In another cost-effective embodiment, which can be manufactured at low costs, the blocking part includes at least two deforming bodies, which act consecutively and can protrude, optionally individually or together, to different extents into the path of displacement of the deformation body. The constructions can also be combined with each other.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.